Micromechanical optical switch

ABSTRACT

An optical switch element is described, which includes a fixed layer disposed outwardly from a substrate and a movable mirror assembly disposed outwardly from the fixed layer. The moveable mirror assembly is operable to move relative to the fixed layer responsive to a voltage applied to the movable mirror assembly. In a particular embodiment, the movable mirror assembly includes an inner strip spaced apart from the fixed layer by a first distance and an outer strip disposed approximately adjacent to the inner strip and spaced apart from the fixed layer by a second distance which is greater than the first distance. The optical transmission of the optical switch element changes depending on the position of the movable mirror assembly.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a continuation of application Ser. No. 10/644,721,by Mohammed N. Islam et al, filed Aug. 20, 2003 now U.S. Pat. No.6,795,605, entitled “Micromechanical Optical Switch.” Application Ser.No. 10/644,721 is a continuation of application Ser. No. 10/227,055, byMohammed N. Islam et al, filed Aug. 22, 2002, entitled “MicromechanicalOptical Switch,” now U.S. Pat. No. 6,654,157. U.S. Pat. No. 6,654,157 isa divisional of application Ser. No. 10/131,744, by Mohammed N. Islam etal, filed Apr. 22, 2002, entitled “Micromechanical Optical Switch,” nowU.S. Pat. No. 6,611,366. U.S. Pat. No. 6,611,366 is a continuation ofapplication Ser. No. 09/631,276, by Mohammed N. Islam et al, filed Aug.1, 2000, and entitled “Micromechanical Optical Switch,” now U.S. Pat.No. 6,407,851.

TECHNICAL FIELD OF THE INVENTION

This invention relates in general to the field of electro-opticalsystems and more particularly to an improved optical switch element andmethods of forming and using the element.

BACKGROUND OF THE INVENTION

The ability to transmit information in the optical domain has greatlyenhanced the speed and bandwidth of data communications. In comparison,the inability to selectively route logical signals that are transmittedin the optical domain has restricted the ability of network designers toaccomplish data communications solely in the optical domain.Accordingly, before a signal can be routed or switched it must first beconverted into electrical signals which can be logically processed usingconventional electrical digital computing systems.

There have been a number of attempts to create a workable optical switcharchitecture which allows for the selective routing of light beamscarrying data communications. Some of these solutions have involved theformation of micromechanical structures using semiconductor processingtechniques. These micromechanical structures typically do not providesuitable speed or reliability for cost-effective commercialapplications. For example, many micromechanical structures suffer fromair damping effects, which increase the required drive voltage and slowthe operation of the device. In addition, these devices have not beentunable to optimize switching speeds according to common packet sizesencountered by the switch.

SUMMARY OF THE INVENTION

Accordingly, a need has arisen for an improved optical switching elementand optical switching system that comprises a structure that can bereliably fabricated and that will operate at switching speeds associatedwith optical data communications.

According to the teachings of the present invention, a micromechanicaloptical switch element is provided that substantially eliminates orreduces problems associated with prior systems.

In accordance with one embodiment of the present invention an opticalswitch element comprises a fixed layer disposed outwardly from asubstrate and a movable mirror assembly disposed outwardly from thefixed layer. The moveable mirror assembly is operable to move relativeto the fixed layer responsive to a voltage applied to the movable mirrorassembly. In one embodiment, the movable mirror assembly includes aninner strip spaced apart from the fixed layer by a first distance and anouter strip disposed approximately adjacent to the inner strip andspaced apart from the fixed layer by a second distance which is greaterthan the first distance. The optical transmission of the optical switchelement changes depending on the position of the movable mirrorassembly.

In accordance with another embodiment of the present invention, anoptical switch element comprises a fixed mirror layer disposed outwardlyfrom a substrate, and a movable mirror assembly comprising an innermirror strip and an outer mirror strip disposed approximately adjacentto and outwardly from the inner mirror strip. In a particularembodiment, the fixed mirror layer and the movable mirror assemblydefine a Fabry-Perot interference cavity, wherein the movable mirrorassembly is operable to move with respect to the fixed mirror layer tochange the reflective or transmissive qualities of the switch element.

In accordance with another embodiment of the present invention, anoptical switch element comprises a fixed layer disposed outwardly from asubstrate, and a unitary movable mirror assembly disposed outwardly fromthe fixed layer and forming with the fixed layer an optical cavity. Themoveable mirror assembly is operable to move relative to the fixed layerin response to a voltage applied to the moveable mirror assembly toaffect a change in the transmissive characteristics of the opticalcavity. The optical switch element is operable to switch between asubstantially transmissive state and a less than substantiallytransmissive state at a rate optimized for a specified packet size.

According to yet another aspect of the invention, a method of forming anoptical switch comprises forming a fixed layer outwardly from asubstrate and forming a movable mirror assembly outwardly from the fixedlayer. In a particular embodiment, the movable mirror assembly comprisesan inner strip disposed outwardly from the fixed layer by a firstdistance and an outer strip disposed approximately adjacent to the innerstrip and spaced apart from the fixed layer by a second distance whichis greater than the first distance. The optical transmission of theoptical switch element changes depending on the position of the movablemirror assembly.

According to still another aspect of the invention, a method ofcommunicating optical signals comprises receiving an optical signal atan optical switch element having a fixed layer and a moveable mirrorassembly disposed outwardly from the fixed layer. In one embodiment, themoveable mirror assembly includes an inner strip spaced apart from thefixed layer by a first distance and an outer strip disposedapproximately adjacent to the inner strip and spaced apart from thefixed layer by a second distance which is greater than the firstdistance. The method further comprises applying a voltage to themoveable mirror assembly to change its position relative to the fixedlayer and cause a change in the optical transmission of the opticalswitch element.

In accordance with another embodiment of the present invention, anoptical switch includes a Mach-Zender interferometer comprising anoptical switch element having a fixed layer disposed outwardly from asubstrate, and a movable mirror assembly disposed outwardly from thefixed layer and operable to move relative to the fixed layer responsiveto a voltage applied to the movable mirror assembly. In a particularembodiment, the movable mirror assembly comprises an inner strip spacedapart from the fixed layer by a first distance; and an outer stripdisposed approximately adjacent to the inner strip and spaced apart fromthe fixed layer by a second distance which is greater than the firstdistance. The optical transmission of the optical switch element changesdepending on the position of the movable mirror assembly.

In accordance with yet another embodiment of the invention, an opticalswitch comprises a pair of collimating lens each having a central axisand each coupled to a fiber so that the axis of each collimating lens isat least partially offset from the axis of the fiber. The switch furthercomprises an optical switch element disposed between the collimatinglenses along the central axis of the fiber and spaced from each of thelenses by approximately a focal length of the respective lens, whereinthe optical switch element is operable to receive optical signals fromone collimating lens and to either transmits those signals to the othercollimating lens or to reflect those signals depending on the positionof a moveable mirror assembly relative to a fixed layer within theswitch element.

In still another embodiment of the present invention, an optical switch,comprises a first optical switch element operable to receive an opticalsignal and a second optical switch element operable to receive anoptical signal, the second optical switch element coupled to the firstoptical switch element over a first mode. The first and second opticalswitch elements coupled to a single mode fiber wherein the first mode atleast partially overlaps the mode of the single mode fiber so thatoptical signals from the first and second switch element couple to thefiber only when the first and second switch elements are substantiallyin phase with one another.

According to another aspect of the invention, an electro-optic routeroperable to receive and switch a plurality of optical signals, therouter comprises a fiber optic tap operable to receive an optical signaland to separate the optical signal into a first signal portion and asecond signal portion. The router further comprises a delay lineoperable to receive the first signal portion and to delay transmissionof the first signal portion until the second signal portion has beenprocessed, and an electronic processor, operable to receive the secondsignal portion, and to perform electronic processing on the secondsignal portion. The router still further comprises an array of opticalswitch elements operable to receive the first and second signal portionsand to perform an optical switching operation on the first and secondsignal portions.

In another aspect of the invention, an electro-optic router is operableto receive a plurality of optical signals and to switch the opticalsignals using an array of optical switch elements. At least one of theoptical switch elements comprises a fixed layer disposed outwardly froma substrate and a movable mirror assembly disposed outwardly from thefixed layer and operable to move relative to the fixed layer responsiveto a voltage applied to the movable mirror assembly. In a particularembodiment, the movable mirror assembly comprises an inner strip spacedapart from the fixed layer by a first distance and an outer stripdisposed approximately adjacent to the inner strip and spaced apart fromthe fixed layer by a second distance which is greater than the firstdistance, wherein the optical transmission of the optical switch elementchanges depending on the position of the movable mirror assembly.

In still another aspect of the invention, a fault tolerant networkcomprises an ingress access node operable to receive an optical signalfrom a network element external to the fault tolerant network. The faulttolerant network further comprises a fault tolerant node operable toreceive the optical signal from the ingress access node and to perform aswitching operation on the optical signal depending on a voltage appliedto an optical switch element within the fault tolerant node, wherein thefault tolerant node allows transmission of the optical signal when novoltage is applied to the switching element.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be acquiredby referring to the accompanying figures wherein like reference numbersindicate like features and wherein:

FIGS. 1A through 1E are greatly enlarged cross-sectional elevationaldiagrams illustrating a method of formation and the operation of anoptical switching element constructed according to the teachings of thepresent invention;

FIG. 2 is a greatly enlarged perspective illustration of a portion of anoptical switching element constructed according to the teachings of thepresent invention;

FIG. 3 is a greatly enlarged cross-sectional elevational diagramillustrating another embodiment of an optical switching elementconstructed according to the present invention;

FIG. 4 is a greatly enlarged cross-sectional elevational diagramillustrating still another embodiment of an optical switching elementconstructed according to the present invention;

FIG. 5 is a greatly enlarged planar diagram of an optical switchingelement constructed according to the teachings of the present invention;

FIGS. 6A and 6B are schematic block diagrams of switching systems, whichmay be constructed according to the teachings of the present invention;

FIGS. 7A-7C are block diagrams showing various 2×2 switch configurationsconstructed according to the teachings of the present invention;

FIG. 8 is a block diagram of an exemplary electro-optic routerconstructed according to the teachings of the present invention; and

FIG. 9 is a block diagram showing an exemplary fault tolerant networkconstructed according to the teachings of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The optical switching element of the present invention is formed on anouter surface of a substrate 10 shown in FIG. 1A. Substrate 10 maycomprise, for example, n-type silicon or indium phosphide. As will bedescribed herein, in one mode of operation, it is advantageous if thesubstrate is optically transmissive in the wavelength range of theoptical signal to be switched by the element. To facilitate that mode ofoperation, in a particular embodiment, a single crystalline siliconsubstrate can be manufactured so that it is optically transmissive inthe range of wavelengths between approximately 1,300 to approximately1,700 nanometers with an optimal transmissive wavelength ofapproximately 1,500 nanometers.

Referring again to FIG. 1A, an antireflective layer 12 is deposited orgrown on an outer surface of the substrate 10. Antireflective layer 12may comprise, for example, a layer of silicon nitride. In theillustrated embodiment, layer 14 is formed to be one-quarter wavelengthin optical thickness. The optical thickness and physical thickness arerelated by the equation $d = \frac{\lambda}{4n}$where d is the physical thickness, n is the index of refraction of thematerial through which the light is passing, and λ is the wavelength ofthe light. For a optimum wavelength of 1.5 microns or 1,500 nanometersand a refractive index of silicon nitride which is equal toapproximately 1.9 at this wavelength, the physical thickness ofantireflective layer 12 will be approximately 2,000 Angstroms. It isadvantageous if the index of refraction of the substrate isapproximately the square of the index of refraction of the materialcomprising antireflective layer 12. The effective optical thickness oflayer 12 can be tuned to more closely approximate one-quarterwavelength, for example, by changing the ratio of silicon and nitrideduring its formation or by changing the physical thickness of thatlayer.

Other materials can be used to form the antireflective layer 12. Forexample, layer 12 may comprise silicon dioxide or other suitabledielectric material or combination of materials. Although antireflectivelayer 12 has been described as having an optical thickness ofone-quarter wavelength, antireflective layer 12 will operate adequatelyat an optical thickness of anywhere between one-eighth of the wavelengthand three-eighths of the wavelength.

Referring again to FIG. 1A, a fixed layer 14 is formed outwardly fromantireflective layer 12. In a particular embodiment where fixed layer 14will comprise part of a Fabry-Perot interference cavity, fixed layer 14comprises a fixed mirror layer formed from an at least partiallyreflective material.

In one embodiment, fixed layer 14 may comprise, for example,polycrystalline silicon (polysilicon) which has been doped sufficientlyto render it at least substantially conductive. Fixed layer 14 may bedoped, for example, using phosphorous or other suitable dopant ordopants. Forming fixed layer 14 from polysilicon facilitates at leastsome transmission of optical signals incident on fixed layer 14 throughsubstrate 10. This construction may be useful, for example, whereelement 10 will be used as an optical switch operating in a pass-throughmode.

In an alternative embodiment, fixed layer 14 may be formed from a metal,such as gold or aluminum, which is substantially reflective of theincident optical signals. This embodiment could be useful, for example,in an optical switch using a non-pass through mode. Where a metal isused to form fixed layer 14, a protective layer may be grown ordeposited outwardly from fixed layer 14.

In the illustrated embodiment, fixed layer 14 is also formed to anoptical thickness of approximately one-quarter wavelength. Where fixedlayer 14 is constructed to provide an optical thickness of approximatelyone-quarter wavelength, the physical thickness of fixed layer 14 will beon the order of 1,000 Angstroms. The relatively smaller physicalthickness of fixed layer 14 results from the relatively larger index ofrefraction of silicon, which is typically on the order of 3.5. Althoughnot shown in the cross-section illustrated in FIG. 1A, suitablepolysilicon conductive structures, bond pads, and other structures maybe created so that a voltage signal can be applied to fixed layer 14.

Referring to FIG. 1B, a number of sacrificial layers are formedoutwardly from fixed layer 14 to provide an interim substrate on whichto form a movable outer mirror assembly. An inner sacrificial layer 16is formed outwardly from fixed layer 14. Layer 16 may comprise, forexample, silicon dioxide deposited to a depth that will eventuallyrepresent the spacing between fixed layer 14 and an inner strip portionof the movable mirror assembly. In a particular embodiment, this spacingdefines an air gap on the order of one-half of a wavelength inthickness. Accordingly, for a 1.5 micron wavelength, the spacing shouldbe on the order of 7,500 Angstroms in depth.

In an alternative embodiment, this air gap could be on the order of onefull wavelength. This embodiment provides an advantage of ensuring thatthe upper mirror assembly 27 does not contact the fixed layer 14 when avoltage is applied between those layers. In that case, inner sacrificiallayer 16 should be formed to a depth of approximately 15,000 Angstromsfor a 1.5 micron wavelength signal. In other embodiments, innersacrificial layer 16 could be formed to any integer multiple number ofone half wavelengths and remain within the scope of this invention.Protective pads, or stops, could also be formed outwardly from fixedlayer 14 and inwardly from the movable mirror layer (to be later formed)to further protect against the moveable mirror assembly 27 contactingfixed layer 14 during operation.

A median sacrificial layer 18 is formed on the outer surface of innersacrificial oxide layer 16. Layer 18 may comprise, for example, a layerof phosphosilicate glass deposited to a depth on the order of 5,000Angstroms. An outer sacrificial oxide layer 20 is formed on the outersurface of layer 18. Outer sacrificial oxide layer 20 may comprise, forexample, a layer of silicon dioxide formed to a depth on the order of2,500 Angstroms.

In the illustrated embodiment, dimensions of layers within the opticalswitching element are selected to provide light transmission through theoptical switching element during a no-voltage condition. In this manner,the invention provides an advantage of facilitating signal passthroughupon an element failure. The illustrated embodiment facilitates thischaracteristic by forming inner sacrificial layer 16 to ultimatelyprovide an air gap that is one half wavelength or an integer multiple ofone-half of one wavelength of the optical signal received.

In another embodiment, the optical switching element could beconstructed to operate in a non-transmissive mode during a no-voltagecondition. For example, inner sacrificial layer 16 can be formed toultimately provide an air gap comprising an odd integer multiple ofone-quarter wavelengths of the optical signal.

The structure formed by sacrificial layer 16, 18 and 20 is patternedusing conventional photolithographic techniques and etched using asuitable plasma assisted fluorine based etchant process to exposeportions of the outer surface of layer 16. As a particular example, ahydrogen fluoride etchant may be used comprising 15 milliliters of 49percent hydrofluoric acid, 10 milliliters of HNO3, and 300 millilitersof water. This reactant will result in an etch rate on the order of 128Angstroms per minute. In another example, a gas mixture for plasmaetching may contain oxygen and trifluoromethane in a pressure ratio onthe order of 6:85. At an RF power of about 28 W, the plasma formed fromthis gas mixture etches 8% LTO at a rate approaching 380 angstroms perminute. Other suitable etching procedures could be used withoutdeparting from the scope of the invention.

The structure resulting from the etch process is shown in FIG. 1B. Itshould be noted that the differing properties of silicon dioxide andphosphosilicate glass result in an undercutting of layer 18 resulting inextensions of layer 20 over and past the borders of layer 18. Forexample, phosphosilicate glass typically etches more quickly thansilicone dioxide in the presence of a fluorine based etchant. Byselecting appropriate materials, amounts, and locations for thesacrificial layers 16-20 as well as an appropriate etchant, etch rate,and temperature, the amount of undercut can be controlled. Thisundercutting is also shown in FIG. 1B. This undercut allows for theself-aligned formation of the outer movable mirror layer strips to occurrelative to the inner strips described previously. The above-describedprocess provides efficiency advantages in manufacture by creating theresulting undercut structure using a single etch.

Referring to FIG. 1C, a movable mirror layer 22, which may comprisepolysilicon doped with a sufficient amount of, for example, phosphorousto render it at least substantially conductive is formed outwardly fromthe exposed portions of layers 16 and 20. Movable mirror layer 22 iscomprised of outer mirror strips, which are exemplified by strips 24 aand 24 b shown in FIG. 1C and inner mirror strips, which are exemplifiedby inner mirror strips 26 a and 26 b shown in FIG. 1C. In theillustrated embodiment, each of outer layer strips 24 and inner layerstrips is formed to a depth on the order of 1,000 Angstroms in thicknessusing the same processes as described with reference to fixed layer 14.

On the periphery of the movable mirror layer 22, the layer 22 isanchored to the substrate by anchor portions 28 and 30. It should beunderstood that anchor portions 28 and 30 are shown in FIG. 1D solelyfor purposes of teaching the structure of the present invention. Inactual construction, a strip is not anchored at its side as shown inFIG. 1C but rather at its ends (not visible in cross-sectional view ofFIGS. 1A-1E). As such, anchors 28 and 30 are actually disposed onopposite ends of the strips as will be discussed and described withreference to FIG. 2 herein.

FIG. 1D illustrates the structure following the removal of thesacrificial layers 16, 18 and 20 using a suitable isotropic oxide etch.The removal of these layers results in a movable mirror assemblyindicated generally at 27 comprising the outer and inner mirror strips24 a, 24 b, and 26 a and 26 b, respectively. The movable mirror assembly27 is operable to move relative to the outer surface of substrate 10 andespecially the outer surface of the fixed layer 14 as shown in FIG. 1E.In this manner, the distance between the fixed layer 14 and the innersurface of the movable mirror strips 24 a-b and 26 a-b changes. Thechange in the distance of this cavity changes the transmissive effectson light that is passing through the assembly 27 and the antireflectivelayer 12 and the substrate 10. Where fixed layer 14 comprises a fixedmirror layer, the resulting interference structure is commonly referredto as a Fabry-Perot cavity.

Throughout this document, the term “assembly” refers to two or morecomponents that collectively form the assembly. Although a particularembodiment of a moveable mirror assembly has been described ascomprising inner and outer strips separated from the fixed mirror layerby different distances, other configurations could be implementedwithout departing from the present invention. For example, the moveablemirror assembly could comprise a plurality of strips that are each asubstantially equal distance from the fixed layer.

In operation of the embodiment shown in FIG. 1, there is an electricalconnection to fixed layer 14 and movable mirror strips 24 a-b and 26a-b. When a voltage is placed between fixed layer 14 and movable mirrorlayer 22, the electrostatic force resulting from such a voltage causesmovable mirror layer 22 to deform toward fixed layer 14. Thisdeformation causes the transmissive quality of the entire structure tochange. For example, in the illustrated embodiment, structures have beenformed to provide an approximately one wavelength air gap between fixedlayer 14 and inner strips 26 a-b, so that the device transmits theoptical signal when no voltage is applied. When a voltage is applied andmovable mirror assembly 27 is pulled toward fixed mirror assembly 14 byapproximately one-quarter of a wavelength, it creates a destructiveinterference effect, reducing the transmission through the opticalelement. It should be understood that deformation by a distance equal toany odd multiple of one-quarter of a wavelength will have the sameinterference effect.

In a particular embodiment, the movement of the moveable mirror assemblyis unitary. In this document, the term “unitary” describes a movement inwhich all of the components operable to move in response to a triggeringevent move when any of those components move. In the particularembodiment implementing a moveable mirror assembly comprising inner andouter strips, the moveable mirror assembly may undergo a unitarymovement causing the inner and outer strips to move substantially inunison. In other embodiments, the components of the moveable mirrorassembly may move independent from one another.

Although the embodiment depicted in FIG. 1E shows deformation of movablemirror assembly 27 toward fixed layer 14, alternative structures couldbe formed to deform movable mirror assembly 27 away from fixed layer 14,creating a similar optical effect. Details of one possible alternatestructure for accomplishing this mode of operation will be describedbelow with respect to FIG. 4.

As discussed above, the optical device shown in FIGS. 1A-1E couldalternatively be constructed to inhibit light transmission during anon-voltage state. For example, the air gap between inner and outerstrips 26 and 24 could comprise an odd integer multiple of one quarterwavelengths, causing destructive interference in the optical cavityduring a no-voltage state. In that case, when a voltage is applied tomovable mirror assembly 27 causing it to move relative to fixed layer 14by one-quarter wavelength, or an odd multiple of one-quarterwavelengths, the light incident on the optical element will experiencepositive interference and be transmitted during an on-voltage state.

Because of the self-aligned formation of inner mirror strips 26 and thespacing between inner mirror strips 26 and the outer mirror strips 24,movable mirror layer 22 is optically equivalent to a smooth planarmirror surface when viewed from a direction perpendicular to the outersurface of the mirror. For example, providing a spacing of an integermultiple of one-half wavelength between the inner and outer movablemirror layers makes the staggered mirror assembly appear to be acontinuous mirror from above. As such, the gaps 32, which help controlair damping of the movement of assembly 27, are provided withoutsubstantially affecting the optical characteristics of the device. In aparticular embodiment, the dimensions of air gaps 32 can be specified toprovide a desired level of air damping. This may, for example, providean additional mechanism for controlling the switching speed of thedevice.

The staggered structure formed by outer mirror strips 24 and innermirror strips 26 results in exhaust gaps indicated at 32 in FIG. 1E.Exhaust gaps 32 allow for air within the optical cavity to be expelledwhen movable mirror layer 22 is deformed relative to fixed layer 14. Ifthe gaps 32 were not present the movement of the movable mirror layer 22would be dampened by the presence of air within the cavity. In theillustrated embodiment, the invention facilitates control of dampingeffects using exhaust gaps 32, without substantially affecting theoptics of the device.

FIG. 2 is a perspective illustration which shows the actual placement ofanchors 28 and 30 at the ends of an outer mirror strip 24 and an innermirror strip 26. FIG. 2 also illustrates the positioning within thestructure of the cross-section which was illustrated with reference toFIGS. 1A through 1E previously. It should be noted that FIG. 2 showsonly a portion of the optical switch element. The outer and inner mirrorstrips 24 and 26, respectively, extend the length of the device and haveanchor bodies (not explicitly shown) such as anchor bodies 28 and 30 oneither end of each strip.

FIG. 3 is a greatly enlarged cross-sectional block diagram of anotherembodiment of an optical switch 100 constructed according to theteachings of the present invention. In this embodiment, the opticalelement 100 includes an anti-reflective layer 112 disposed outwardlyfrom a substrate 110. Anti-reflective layer 112 is similar in structureand function to anti-reflective layer 12 discussed with reference toFIG. 1.

Optical element 100 further includes a fixed layer stack 119 disposedoutwardly from anti-reflective layer 112. Fixed layer stack 119 issimilar in function to fixed layer 14 of FIG. 1. However, rather thanimplementing only a single fixed layer, fixed layer stack 119 utilizesmultiple alternating layers of polysilicon and dielectric material. Inthis example, fixed layer stack 119 includes an interstitial fixed layer115 disposed between a first fixed layer 114 and a second fixed layer117. Additional alternating layers could be added without departing fromthe scope of the invention. Using one or more multilayer stacks to formfixed layer stack 119 provides an advantage of increasing thereflectivity of the assembly 119. This, in turn, increases the contrastratio of the transmissive state of element 100, allowing for a higherfinesse optical cavity, particularly where the cavity is a Fabry-Perotcavity.

In this example, first and second fixed layers 114 and 117 each haveoptical thicknesses of approximately one quarter wavelength of theoptical signal to be switched. As a particular example, each of firstand second fixed layers 114 and 117 could comprise approximately 1000Angstroms of polysilicon doped sufficiently to render them at leastsubstantially conductive. Interstitial fixed layer 115 could comprisesapproximately 2000 Angstroms of silicon nitride.

Optical device 100 further includes a movable mirror assembly 122disposed outwardly from fixed layer stack 119. Movable mirror assembly122 includes inner strips 126 and outer strips 124. In the illustratedembodiment, each inner strip 126 includes an inner polysilicon layer130, an interstitial layer 132 disposed outwardly from inner polysiliconlayer 130, and an outer polysilicon layer 134 disposed outwardly frominterstitial layer 132. Polysilicon layers 130 and 134 may eachcomprise, for example, polysilicon that has been doped sufficiently torender it at least substantially conductive. An appropriate dopant maycomprise, for example, phosphorous.

Interstitial layer 132 may comprise, for example, silicon nitride orother suitable dielectric material or combination of materials. In theexample shown in FIG. 3, outer strip 124 includes an inner polysiliconlayer 140, an interstitial layer 142 disposed outwardly from innerpolysilicon layer 140, and an outer polysilicon layer 144 disposedoutwardly from interstitial layer 142. Layers 140-144 of outer strip 124in this example are similar in structure and function to layers 130-134,respectively, of inner strip 126, For example, layers 140 and 144 maycomprise doped polysilicon and interstitial layer 142 may comprisesilicon nitride.

In this example, each of layers 130-134 and 140-144 is formed to providean optical thickness of one-quarter of a wavelength of the opticalsignal received by element 100. In this example, polysilicon layers 130,134, 140, and 144 each comprises approximately 1000 Angstroms.Interstitial layers 132 and 142 each comprises approximately 2000Angstroms of silicon nitride. Although the illustrated embodiment showsa moveable mirror assembly having a stack of three alternatingpolysilicon and interstitial layers, additional alternating layers ofpolysilicon and dielectric material could be used without departing fromthe scope of the invention. Like the multi-layer stacks used to formfixed layer stack 119, the multilayer stacks forming strips 124 and 126provide increased reflectivity, better contrast ratios, and a higherfinesse optical cavity.

FIG. 4 is a greatly enlarged cross-sectional elevational diagramillustrating another embodiment of an optical switching element 200constructed according to the teachings of the present invention. Element200 is similar in structure and function to element 100 shown in FIG. 3.Element 200 shown in FIG. 4 includes an inner fixed layer 214 disposedoutwardly from an anti-reflective layer 212 and a substrate 210. Element200 also includes a movable mirror assembly 222 disposed outwardly frominner fixed layer 214. Movable mirror assembly 222 includes one or moreinner strips 226 and one or more outer strips 224. In this embodiment,inner strip 226 comprises a thickness d1 and outer strip 224 comprises athickness d2. In this example, the thickness d1 of inner strip 226 isgreater than thickness d2 of outer strip 224. By using differentthicknesses for the inner and outer strips of movable mirror assembly224, the contrast ratio of the device can be improved. Although theillustrated embodiment shows thickness d1 of inner strip 226 as beinggreater than thickness d2 of outer layer 224, the thickness d2 of outerstrip 224 could be greater than thickness d1 of inner strip 226.

In this particular embodiment, element 200 includes an outer fixed layer230 disposed outwardly from moveable mirror assembly 222. Second fixedlayer 230 can be formed, for example, with polysilicon formed to athickness of approximately one quarter wavelength of the optical signalreceived. Second fixed layer 230 may be doped to render it at leastsubstantially conductive. Outer fixed layer 230 is separated frommoveable mirror assembly 222 by an air gap of one half wavelength of theoptical signal received. The air gap could alternatively comprise anyinteger multiple of signal wavelengths. Providing an air gap of one fullwavelength provides an advantage of ensuring that the moveable mirrorassembly 222 will not contact the outer fixed layer 230 duringoperation.

In operation of this embodiment, a voltage can be applied betweenmoveable mirror assembly 222 and outer fixed layer 230. This voltagecauses moveable mirror assembly 222 to deform toward outer fixed layer230 and away from inner fixed layer 214, which changes the transmissiveor reflective characteristics of the device. For example, the air gapsand layer thicknesses can be selected to provide a substantiallytransmissive state when no voltage is applied between moveable mirrorassembly and outer fixed layer, and a less than substantiallytransmissive state when a voltage is applied between those layers.

In a particular embodiment, a first voltage may be applied betweenmoveable mirror assembly 222 and outer fixed layer 230 to cause moveablemirror assembly 222 to deform away from inner fixed layer 222. At anappropriate time, and a second voltage can be applied between moveablemirror assembly 222 and inner fixed layer 214 to cause moveable mirrorassembly 222 to deform toward inner fixed layer 214. Through a suitablecombination of alternating voltage applications, optical element 200 canbe forced to switch between substantially transmissive and lesstransmissive states. Using alternating voltages to switch the opticalcharacteristics of the device can result in even faster switching ratesthan single voltage approaches.

The present invention contemplates the use of some, all, or none of theabove described features of stacked fixed and mirror layers, inner andouter moveable mirror layers, varying strip thicknesses, and inner andouter fixed layers. An optical switch element within the scope of thisinvention could be constructed using any combination of some, all, ornone of these particular characteristics.

FIG. 5 illustrates a planar view of one possible embodiment of anoptical switching element. The element comprises a plurality of stripsthat are alternatively inner and outer mirror strips such as strips 24and 26 discussed previously. In this particular example, the element isapproximately square and on the order of 100 to 500 microns on a side.FIG. 5 also illustrates the placement of an optical beam indicated at 34in FIG. 5. A typical optical beam will be approximately 100 to 150microns in diameter. The element indicated at 36 in FIG. 5 isapproximately twice the size on a side as the diameter of the beam 34.Accordingly, the length of each strip would be on the order of 100 to500 microns in length. Further, if each strip is on the order of 2microns in width, there would be approximately 100 strips if the element36 was 200 microns on a side. Although particular shapes and dimensionshave been described with respect to the element shown in FIG. 5, any ofa variety of component configurations and dimensions could alternativelybe implemented without departing from the scope of the invention.

The optical switching element of the present invention enjoys thebenefit that the gaps 32 allow for extremely fast operation of thedevice while controlling air damping of the movement of the movablemirror layer 22. Further, the fact that the movable mirror is formed inparallel offset strips provides for uniform voltage distribution acrossthe entire element. The flow of energy as the voltage potential buildson the movable mirror layer is made a great deal more uniform by theparallel strips than it would be if the movable mirror layer was asingle plate of conductive material. The movable mirror strips areformed so that they are under a preset amount of tension. The length ofthe strips, their thickness and width, can be kept small so that eachstrip has a very low individual mass. A strip that is under a largeamount of tension and has a low mass will have a correspondingly higherresonant frequency. The speed at which the device operates is greatlyenhanced by a high resonant frequency within the movable element.

By appropriate selection of, for example, material type, amounts ofmaterials, strip dimensions, and/or strip tension, the inventionfacilitates tuning of switching speeds to maximize switching efficiency.This can be extremely useful in tuning switching speeds to correspondto, for example, common information packet sizes.

For example, the following table shows IP packet sizes in bytes and thetotal number of packets percent bytes during the years 1998 and 1999.

PACKET SIZE TOTAL PACKETS TOTAL BYTES (IN BYTES) (%) (%) 40 38.9 4.41,500 11.5 48.7 552 10.1 15.8 44 6.1 0.8 576 4.9 7.9

This data shows that almost fifty percent of IP packets are between 40and 44 bytes long. Assuming a data rate of 2.5 Gigabytes per second,switching these packets takes approximately 128 nanoseconds. Thus, forcurrent packet sizes and data rates, a switching speed of approximately100 nanoseconds is desirable. Existing switching technologies are eithertoo expensive, or too slow for this application. For example, LithiumNiobate, semiconductor optical amplifiers, or electro-absorptionmodulators can switch in less than one nanosecond, a rate much fasterthan the optimal 100 nanosecond rate. These devices are prohibitivelyexpensive, particularly when compared to the present invention. Inaddition, these devices tend to be polarization sensitive. Liquidcrystal devices, thermo-optic devices, and micro-electro-optic switchesusing a single continuous membrane as a moveable mirror are capable ofswitching speeds of only up to one microsecond, too slow for optimaloperation.

The present invention facilitates tuning the optical switch element toprovide a variety of switching speeds. In a particular embodiment, theswitch element can be tuned to provide a switching speed commensuratewith a specified packet size or range of packet sizes. For example, theswitch element can be tuned to provide switching speeds commensuratewith average packet sizes encountered by the switch element. The presentinvention facilitates switching speeds of up to 10 nanoseconds, and canbe tuned to provide an optimum switching speed of, for example,approximately 100 to 300 nanoseconds.

FIG. 6A illustrates one architecture of an optical switching system thatmay utilize switching element 36 constructed according to the teachingsof the present invention. FIG. 6A illustrates a switching element 40which is placed at an angle to an optical beam 42 and which selectivelydirects optical beam 42 to a first receiver 44 or a second receiver 46using the switching element 36. In the illustrated embodiment, when theswitching element 36 is in its undeformed state the mirror strips 24 and26 are in their furthest position from fixed layer 14. In this state, asdescribed previously, the switching element 36 is optically transmissiveand the beam 42 will pass through element 36 and strike receiver 46.Optionally, a voltage can be placed between fixed layer 14 and movablemirror layer 22 causing the movable mirror layer 22 to deform towardsthe fixed layer 14. In this state, element 36 will reflect optical beam42 toward receiver 44. In this manner, the beam 42 can be switchedbetween receiver 44 and 46.

FIG. 6B illustrates an additional embodiment of a switching system,indicated generally at 48, which also utilizes switching element 36.Switching system 48 comprises a first receiver 50 and a second receiver52. Switching system 48 is operable to switch an optical beam 54 whichfirst passes through a circulator system 56. Optical beam 54 then eitherreflects off of element 36 or passes through element 36 to receiver 52.If element 36 is in its reflective, deformed state, optical beam 54returns to circulator 56 where the returning beam is directed towardsreceiver 50. Circulator system 56 is operable to receive and deflect anyreflected signal. In this manner, system 48 selectively routes beam 54to either receiver 50 or 52 depending on whether or not element 36 isactivated. System 48 does not require element 36 to be at an anglecompared to the path of beam 54 as required with system 40 describedwith reference to FIG. 6A previously.

The examples described in FIGS. 6A and 6B assume a single fixed layerand a voltage applied between the fixed layer 14 and the movable mirrorassembly 27 to deform moveable mirror layer 27 towards fixed layer 14.Of course, an outer fixed layer 230 could also, or alternatively beimplemented and a voltage applied between moveable mirror assembly 27and the outer fixed layer 230 to deform moveable mirror assembly 27 awayfrom fixed layer 14, accomplishing a similar optical effect.

FIGS. 7A-7C are block diagrams showing various 2×2 switchconfigurations.

FIG. 7A is a block diagram showing a Mach-Zender based switch 300implementing optical switch elements such as those depicted in FIGS. 1,3, and/or 4. Switch 300 includes an interferometer 310. Interferometer310 may comprise, for example, a fiber or a waveguide Mach-Zenderinterferometer. Optical switch elements 312 and 314 are coupled tointerferometer 310 and receive incident optical signals at inputs 316and 318, respectively. Depending on whether moveable mirror assembly 22of each switching element 312 and 314 is in a deformed or a non-deformedstate, optical switch elements 312 and 314 will transmit or reflect theincident optical signals. In a transmissive state, output 320 of switch300 receives transmitted input 316, and output 322 receives transmittedinput 316. In a reflective mode of operation, output 320 receivesreflected input 316 and output 322 receives reflected input 318.

In another mode of operation, a relative phase between the two arms ofthe Mach-Zender interferometer can be used to switch the device. Forexample, a variable relative phase between the two arms of theinterferometer can cause constructive or destructive interference,resulting in either an on or an off state.

FIG. 7B is a block diagram of an optical switch 350 using a Mach-Zenderstructure coupled to a single mode fiber. Switch 350 includes opticalswitch elements 352 and 354 coupled to a single mode fiber 360. In thisembodiment, a Mach-Zender interferometer is implemented by overlappingthe mode of fiber 360 with the mode of the fiber through switch elements352 and 354. In operation, if switch elements 352 and 354 are in phase,then the phase pattern is symmetric and it couples to fiber 360. A phasedifference of say, 180 degrees gives rise to an anti-symmetric mode,which prevents coupling between fiber 360 and switch elements 352 and/or354.

In a particular embodiment, a phase difference between switch elements352 and 354 can be achieved by causing the moveable mirror assemblies inthose elements deform in opposite directions. In this way, a switchingphase difference can be achieved with minimal deformation of eachmoveable mirror assembly. This minimal deformation results in lowerdrive voltages, and faster operation.

FIG. 7C is a block diagram showing yet another embodiment of a 2×2switch. Switch 400 includes an optical switch element 410 positionedbetween two collimating lenses 420 and 430. Lenses 420 and 430 arespaced from switching element 410 by approximately the focal length oflenses 420 and 430. Inputs 422 and 423 are symmetrically placed slightlyoff axis from axis 425 of lenses 420 and 430, respectively. When switchelement 410 is in a substantially transmissive mode, inputs received atinput 422 are communicated to output 434, and inputs received at input432 are communicated to output 424. When switch element 410 is inreflective mode, inputs received at input 422 are reflected to output424, and inputs received at input 432 are reflected to output 434.

An N×N switch can be formed from a plurality of 2×2 switching blocks,such as switches 300, 350, and/or 400. The NxN switch could beconfigured, for example, as a crossbar switch or an N-stage planarswitch.

In accordance with the teaching of the present invention a switchingelement and switching systems are described that provide for either asubstantially transmissive state or a less transmissive state dependingon whether or not a movable mirror assembly is deformed relative to afixed layer. The movement of the movable mirror assembly affects theinterference characteristics of an optical cavity between the fixedlayer and the moveable mirror assembly. In one embodiment, the moveablemirror assembly includes segmented strips which provide for escape gapsfor air to escape from the optical cavity the moveable mirror assemblydeforms and restores. The strips have a relatively low mass and can beplaced under a pre-selected tension to derive a desired resonantfrequency and associated switching speed. For example, the presentinvention facilitates switching speeds on the order of 10 nanoseconds,and may be tuned to provide switching speeds of approximately 100nanoseconds.

FIG. 8 is a block diagram of an exemplary electro-optic router 500constructed according to the teachings of the present invention.Electro-optic router 500 may include one or more optical amplifiers 510.In the illustrated embodiment, an optical amplifier 510 resides at theingress end of the router, which receives optical signals 512 over acommunication link 520. Electro-optic router 500 could also oralternatively include optical amplifiers at the egress end of therouter, or at various other points within the router. Optical amplifiers510 compensate for losses in the signal and line rates of, for example,OC-48 and OC-192 or higher. In the illustrated embodiment, communicationlink 520 comprises a single mode fiber carrying, for example, 100wavelengths ranging from 1500 to 1600 nanometers and 2.5 Gb/s perchannel.

Optical signal 512 comprises header information 514 and signal payload516. Electro-optic router includes a fiber optic tap operable tocommunicate a first portion of optical signal 512 to a delay line 522and a second portion of optical signal 512 to a demultiplexer 524. Inthe illustrated embodiment, demultiplexer 524 may comprise, for example,a wavelength grating router, operable to split the incoming signal intoa plurality of wavelengths and send the plurality of wavelengths to anarray of wavelength detectors 526.

Electro-optic router 500 also includes an electronic processor 528operable to receive optical signals from detectors 526, to convert theoptical signals to electronic signals, and perform various switching,routing, or other processing functions on the converted electronicsignals. Electronic processor 528 is further operable to convertprocessed electronic signals into optical signals for transmission to aswitching array 530.

Electro-optic router 500 further includes a demultiplexer coupled todelay line 522. In this embodiment, demultiplexer 532 comprises one ormore wavelength grating routers. Both demultiplexer 532 and electronicprocessor 528 communicate with a switching array 530. In this example,switching array 530 comprises an array of micromechanical opticalswitching elements, such as those described with respect to FIGS. 1-6.

Switching array 530 receives processed optical header information fromelectronic processor 528 and optical payload information from delay line522, and performs various switching functions on those signals. Amultiplexer 536 receives switched optical signals from switching array530 and transmits switched optical signals 540 to other networkelements.

In operation, electro-optical router 500 receives a plurality of opticalsignals 512 and depending on, for example, the signal and line rates,may amplify those signals at optical amplifier 510. Fiber optic tap 518receives optical signals 512 and taps header information 514 fromoptical signals 512. Header information 514 is passed to demultiplexer524, while payload information 516 is communicated to delay line 522.Delay line 522 serves as a first-in-first-out (FIFO) buffer. The FIFObuffer length is set so as to provide enough time for electronicprocessor 528 to process the various header information 514.

While payload information 516 is delayed in FIFO buffer 522, electronicprocessor 528 converts optical header information 514 into electronicsignals, and performs various processing on that header information.After completing processing of the electronic header information,electronic processor 528 converts the electronic header information backinto one or more optical signals and transmits those signals toswitching array 530.

Switching array 530 receives processed header information andunprocessed payload information 516, and associates the related payloadand header information. Optical switching array 530 then switches theprocessed optical signals at rates ranging, for example, fromapproximately 10 to 100 nanoseconds or longer. Multiplexer 536 receivesswitched optical signals 540 from switching array 530 and transmits theswitched optical signals to other network elements.

By transmitting the optical payload information transparently toelectronic processor 528, electro-optical router 500 advantageouslyfacilitates field coding. As such, header information can beelectronically processed at rates on the order of 2.5 Gigabytes persecond, while transparent optical payload information communicates atrates of 10 Gigabytes per second or higher. Electro-optic router 500also facilitates parallel processing of multiple wavelength channels,increasing the speed and efficiency of the router. In a particularembodiment, differential logic such as Manchester coding can be used tocompensate for switching contrast ratio.

In a particular embodiment, switching array 530 comprises optical switchelements that are substantially transmissive of optical signals while ina no-voltage state, and less transmissive of the optical signals when avoltage is applied. For example, switching array 530 may include opticalswitch elements, such as those shown in FIG. 1, where the air gapbetween the fixed layer 14 and the movable mirror assembly 22 during ano voltage state is an even integer multiple of one quarter wavelengthsof the optical signal. In this manner, the switch elements remaintransmissive during a failed condition, creating a fault tolerantoptical switching device.

FIG. 9 is a block diagram showing an exemplary fault tolerant network600 constructed according to the teachings of the present invention.Fault tolerant network 600 includes a fiber core 610 comprising two ormore edge nodes 612-616 coupled to at least one fault tolerant node 620by communication links 618 operable to facilitate communication ofoptical signals. In this example, communication links 618 comprisesingle mode optical fibers. Communication links 618 could, however,comprise another medium operable to facilitate transmission of opticalsignals comprising one or a plurality of wavelengths.

In the illustrated embodiment, signals communicated through fiber core610 pass through fault tolerant node 620. Although the illustratedembodiment shows a single fault tolerant node 620, fiber core 610 couldalternatively comprise any number of fault tolerant nodes coupled to oneor more edge nodes and arranged in a variety of configurations. Forexample, multiple fault tolerant nodes 620 could be arranged in a ringconfiguration, a star configuration, or any other configuration suitableto route and communicate optical signals through fiber core 610.

In this example, each of edge nodes 612-616 comprises an access routeroperable to receive electrical and/or optical signals and to convert theelectrical signals into optical signals for transmission over fiber core610. Edge nodes 612-616 provide electronic buffering until the signal isready to be placed onto the optical backbone 618.

Edge nodes 612-616 may also examine header data of signals received fromcommunication links 622-626 to identify a signal path through all orpart of fiber core 610 toward a destination network element coupled tofiber core 610. Accordingly, edge nodes 612-616 attach a destinationaddress to the data and frame or encapsulate the data for transmissionacross fiber backbone 618. Edge nodes receiving encapsulated data ategress points from fiber core 610 remove the framing that was attachedat the ingress edge node and facilitate transmission of the signaltoward a destination external network element. For example, where thesignal received at the ingress edge node was an electrical signal,egress edge node 612-616 converts the optical signal received fromoptical backbone 618 to an electrical signal for transmission toward adestination external network element in an electrical format.

In this embodiment, fault tolerant node 620 comprises an electro-opticrouter, such as electro-optic router 500 shown in FIG. 8. In theembodiment shown here, fault tolerant node 620 comprises anelectro-optic router having switch elements that are substantiallytransmissive of optical signals when no voltage is applied to the switchelement. Some or all of edge nodes 612-616 could also comprise faulttolerant circuitry without departing from the scope of the invention.

In a particular embodiment, fault tolerant node 620 may comprise switchelements, such as those shown in FIG. 1, designed to provide ano-voltage air gap between fixed layer 14 and movable mirror layer 22equal to an even integer multiple of one quarter of a wavelength of theoptical signal. This design allows transmission of optical signalsduring a no-voltage state or during a failure state. In this way, fibercore 610 facilitates fault tolerant operation by passing optical signalsin the event of a node failure.

In operation, each of edge nodes 612-616 communicates with one or moreexternal network elements via communication links 622-666, respectively.Ingress edge nodes of fiber core 610 receive electrical and/or opticalsignals from communication links 622-626, convert the electrical signalsto optical signals, determine destination addresses associated with thesignals, frame the signals appending the destination addresses to thesignals, and route the optical signals toward an egress edge node offiber core 610.

Signals traversing fiber core 610 pass through one or more faulttolerant nodes 620. Each fault tolerant node 620 routes the opticalsignals toward the egress edge node using its switching array. Theswitch elements of fault tolerant nodes 620 operate in a substantiallytransmissive state when no voltage is applied, and in a lesstransmissive state when a voltage is applied between a fixed mirrorsurface and a moveable mirror assembly. In this way, fiber core 610operates to facilitate pass through operation in the event of a faultwithin fiber core 610.

Although the present invention has been described in detail it should beunderstood that various changes, alterations, substitutions, andmodifications may be made to the teachings described herein withoutdeparting from the spirit and scope of the present invention which issolely defined by the appended claims.

1. A fault tolerant network, comprising: an ingress access node operableto receive an optical signal from a network element external to thefault tolerant network; and a fault tolerant node operable to receivethe optical signal from the ingress access node and to perform aswitching operation on the optical signal depending on a voltage appliedto an optical switching element within the fault tolerant node, whereinthe fault tolerant node allows transmission of the optical signal whenno voltage is applied to the optical switching element.
 2. The faulttolerant network of claim 1, wherein the ingress access node is furtheroperable to receive an electronic signal from a network element externalto the fault tolerant network, and to convert the electrical signal toan optical signal.
 3. The fault tolerant network of claim 1, wherein theoptical switch elements comprises a fixed layer disposed outwardly froma substrate; and a unitary moveable mirror structure disposed outwardlyfrom the fixed layer and forming with the fixed layer a cavity, themoveable mirror structure operable to move relative to the fixed layerin response to a voltage applied to the moveable mirror structure toaffect a change in a characteristic of the optical switch element. 4.The fault tolerant network of claim 3, wherein the optical switchelement is operable to change between a substantially transmissive stateand a less than substantially transmissive state in response to theapplied voltage.
 5. The fault tolerant network of claim 3, wherein theoptical switch element is operable to change between a substantiallyreflective state and a less than substantially reflective state inresponse to the applied voltage.
 6. The fault tolerant network of claim3, wherein the optical switch element is capable of moving relative tothe fixed layer within 30 microseconds in response to the appliedvoltage.
 7. An optical processing device comprising: a demultiplexeroperable to receive a multiple wavelength optical signal and to selectat least one of the optical signal wavelengths; a plurality of lenseseach having a central axis and each capable of receiving at least aportion of the at least one selected optical signal wavelength; at leastone optical switching element disposed between a first lens and a secondlens of the plurality of lenses, wherein the at least one opticalswitching element comprises: a fixed layer disposed outwardly from asubstrate; and a unitary moveable mirror structure disposed outwardlyfrom the fixed layer and forming with the fixed layer a cavity, theunitary moveable mirror structure operable to move relative to the fixedlayer in response to a voltage applied to the unitary moveable mirrorstructure to affect a change in a characteristic of the opticalswitching element; and wherein the at least one optical switchingelement is operable to receive the portion of the at least one selectedoptical signal wavelength from the first lens of the plurality of lensesand to reflect the portion of the at least one selected optical signalwavelength to the second lens of the plurality of lenses depending onthe position of the unitary moveable mirror structure relative to thefixed layer.
 8. The optical processing device of claim 7, wherein the atleast one optical switching element comprises an array of optical switchcomponents; and wherein at least one of the array of optical switchingcomponents is at least partially offset from the central axis of one ormore of the plurality of lenses.
 9. The optical processing device ofclaim 7, wherein the substrate is a semiconductor substrate thatincludes a material selected from the group consisting of silicon andindium phosphide.
 10. The optical processing device of claim 7, whereineach lens of the plurality of lenses comprises a collimating lenscapable of shaping a beam of light corresponding to the at least oneselected optical signal wavelength.
 11. The optical processing device ofclaim 7, wherein the at least one optical switching element is spacedfrom each of the plurality of lenses by approximately a focal length ofthe respective lens.
 12. The optical processing device of claim 7,wherein the optical switch element is capable of moving relative to thefixed layer within 30 microseconds in response to the applied voltage.13. The optical processing device of claim 7, wherein the change in thecharacteristic of the optical switching element provides a functionselected from the group consisting of a binary optical switchingfunction, a variable optical attenuator function, and a modulationfunction.
 14. The optical processing device of claim 7, wherein themotion of the unitary moveable mirror structure is approximatelyparallel to the fixed layer.
 15. The optical processing device of claim7, further comprising an optical tap operable to receive the multiplewavelength optical signal and to separate the multiple wavelengthoptical signal into a first signal portion and a second signal portion.16. The optical processing device of claim 7, wherein the voltageapplied to the moveable mirror structure is generated by an electronicprocessor.
 17. The optical processing device of claim 16, wherein theelectronic processor comprises a plurality of controllers, eachcontroller operable to control at least one of the optical switchingelements.
 18. A method of communication optical signals, comprising:selecting at least one of a plurality of optical signal wavelengths;receiving at least a portion of the at least one selected optical signalwavelength at a first lens of a plurality of lenses; receiving theportion of the at least one selected optical signal wavelength at anoptical switching element comprising a fixed layer and a unitarymoveable mirror structure disposed outwardly from the fixed layer, thefixed layer and the unitary moveable mirror layer forming a cavity;applying a voltage to the optical switching element to change theposition of the unitary moveable mirror structure relative to the fixedlayer and cause a change in a characteristic of the optical switchingelement; and wherein the at least one optical switching element isoperable to reflect the portion of the at least one selected opticalsignal wavelength to a second lens of the plurality of lenses dependingon the position of the unitary moveable mirror structure relative to thefixed layer.
 19. The method of claim 18, wherein each of the first lensand the second lens has a central axis.
 20. The method of claim 18,wherein each of the first and second lenses comprises a collimating lenscapable of shaping a beam of light corresponding to the at least oneselected optical signal wavelength.
 21. The method of claim 18, whereinthe optical switching element is spaced from each of the first lens andthe second lens by approximately a focal length of the respective lens.22. The method of claim 18, wherein the optical switch element iscapable of moving, relative to the fixed layer within 30 microseconds inresponse to the applied voltage.
 23. The method of claim 18, wherein thechange in the characteristic of the optical switching element provides afunction selected from the group consisting of a binary opticalswitching function, a variable optical attenuator function, and amodulation function.
 24. The method of claim 18, further comprising:receiving an input signal comprising the plurality of optical signalwavelengths at an optical tap; and separating the input signal into afirst signal portion and a second signal portion.
 25. The method ofclaim 18, wherein the unitary moveable mirror structure is approximatelyparallel to the fixed layer after the change in position of the unitarymoveable mirror structure.
 26. A method of communication opticalsignals, comprising: selecting at least one of a plurality of opticalsignal wavelengths; receiving at least a portion of the at least oneselected optical signal wavelength at a first lens of a plurality oflenses; receiving the portion of the at least one selected opticalsignal wavelength at an optical switching element comprising a fixedlayer and a unitary moveable mirror structure disposed outwardly fromthe fixed layer, the fixed layer and the unitary moveable mirror layerforming a cavity; applying a voltage to the optical switching element tochange the position of the unitary moveable mirror structure relative tothe fixed layer and cause a change in a characteristic of the opticalswitching element; and wherein the at least one optical switchingelement is operable to communicate the portion of the at least oneselected optical signal wavelength to a second lens of the plurality oflenses when the unitary moveable mirror structure is in a first positionrelative to the fixed layer, and wherein the second lens does notreceive the portion of the at least one selected optical signalwavelength when the unitary moveable mirror structure is in a secondposition relative to the fixed layer.
 27. An optical processing devicecomprising: a demultiplexer operable to receive a multiple wavelengthoptical signal and to select at least one of the optical signalwavelengths; a first lens of a plurality of lenses, the first lensoperable to receive at least a portion of the at least one selectedoptical signal wavelength; at least one optical switching elementdisposed between the first lens and a second lens of the plurality oflenses, the at least one optical switching element operable to receivethe portion of the at least one selected optical signal wavelength fromthe first lens, wherein the at least one optical switching elementcomprises: a fixed layer disposed outwardly from a substrate; and aunitary moveable mirror structure disposed outwardly from the fixedlayer and forming with the fixed layer a cavity, the unitary moveablemirror structure operable to move relative to the fixed layer inresponse to a voltage applied to the unitary moveable mirror structureto affect a change in a characteristic of the optical switching element;and wherein the at least one optical switching element is operable tocommunicate the portion of the at least one selected optical signalwavelength to the second lens of the plurality of lenses when theunitary moveable mirror structure is in a first position relative to thefixed layer, and wherein the second lens does not receive the portion ofthe at least one selected optical signal wavelength when the unitarymoveable mirror structure is in a second position relative to the fixedlayer.